1. Field of the Invention:
The present invention relates to a structure of an optical system lens fine adjustment apparatus which finely varies the focal length of an optical system lens employed in an optical system precision device or a camera, such as an automatic focusing camera, a video camera and so forth.
2. Description of the Prior Art:
As a means for varying the focal length of a lens, a permanent magnet and a coil are employed to make use of electromagnetic force to displace the lens. This means, however, offers the following disadvantages. The employment of a permanent magnet and a coil unfavorably complicates the structure of the apparatus for carrying out the focal length variation and increases the size thereof as well as results in large variations in conditions among various apparatuses. In addition, with the conventional techniques, it has been difficult to effect fine positioning of the lens.
Another conventional techniques of varying the position of a lens employs a vibrator constituted by a piezoelectric material. In this case, if the vibrator is constituted by a piezoelectric film of, for example, PVF.sub.2, it is necessary to firmly secure the outer edge portion of the vibrator for the purpose of preventing the vibrator from being deflected by the weight of the lens, which involves difficulty in aligning optical axes with each other. Further, it is difficult for the vibrator of the type described above to vibrate with a large amplitude. On the other hand, a vibrator of piezoelectric ceramic inconveniently involves difficulty in supporting and securing the same and has the disadvantage that the vibration mode and the displacement amount undesirably change depending upon various conditions including the position at which the vibrator is secured.